Huntsman: "This is not about ratings for Donald Trump, this is about jobs for the American people. This is a serious debate that we ought to be having here in the United States," he said on NBC's Today. "I believe that the presidency of the United States of America is beyond reality shows. This is a joke."

Robert Gibbs: “Cancel Christmas. Just get ready for the Donald Trump debate," said the former White House spokesperson on Morning Joe, according to Politico. "Pay-per-view. Pay-per-view. We ought to have this, the new rule, I think you’ve heard, you have to have your birth certificate to participate in the debate. It’s like shooting fish in a barrel."

Michele Bachmann: Yes, even Bachmann admits that there is some "concern" over Trump's debate, specifically because he plans to endorse a candidate and is already "leaning toward" one. Will she attend? Her campaign is "still in the process" of deciding, she said on the Early Show, adding that she has "great respect for Donald Trump."

John McCain: "I do think that on Dec. 27, on an obscure network, I wonder if that is the best use of the candidates’ time," the senator told Fox News today, according to Politico. "I think they should be resting up over Christmas and the next few days and be ready to go right after the first of January."

Karl Rove: Also on Fox News, he wondered last night, "How can we have any confidence [Trump is] going to be impartial in his questions? We’ve got a guy who’s not only saying, I am going to make a decision about who I am going to endorse shortly after this debate and I am already leaning some way and I may run myself. And we expect him to be the impartial moderator at this debate?"

But Trump hit back at Rove and also conservative commentator Charles Krauthammer, who called the debate a "reality TV show" and a "joke," insisting that they and others who have criticized him are "hacks," Politico reports. Click to see who's defending Trump.